September 11. Rhynchocephalians

There were plenty of other reptile lineages evolving during the Triassic besides the archosaurs and their descendents, the dinosaurs. One group, the rhynchocephalians, became quite diverse soon after they emerged in middle Triassic time. They were reptiles covered with overlapping scales, in contrast to the other large group of reptiles, the archosaurs, which had more flexible skin and other coverings, including feathers in birds.  

Homoeosaurus, a rhynchocephalian. Photo by Haplochromis under GFDL 

The parent group to the rhynchocephalians also includes snakes and most lizards, but despite their abundance and diversity during the Triassic and later Mesozoic, only two species of rhynchocephalian survive today – two varieties of the tuatara of New Zealand, the only reptile native to New Zealand. It’s a large, 3-foot-long lizard-like reptile. As the only survivor of the rhynchocephalian order, its heritage goes back a long way and information about the tuatara may be significant to our understanding the evolution of snakes, dinosaurs, and birds.

The name rhynchocephalia means “beak-head” for various bony plates found on the skulls of the animal.

—Richard I. Gibson

Photo by Haplochromis under GFDL